The Forestry Forum

Other topics for members => General Woodworking => Topic started by: Tony on July 30, 2007, 02:00:19 PM

Title: bubbles in polyurethane
Post by: Tony on July 30, 2007, 02:00:19 PM
      how to remove bubbles from polyed project? ??? ::) ???

      how to prevent future bubbles? ??? ::) ???

                       Tony  8)
Title: Re: bubbles in polyurethane
Post by: bedway on July 30, 2007, 02:03:39 PM
If your shakeing it, vrs. stirring it prior to application, thats your problem,,bedway
Title: Re: bubbles in polyurethane
Post by: Dodgy Loner on July 30, 2007, 02:17:30 PM
Lots of things could cause bubbles in your finish.  Like bedway says, poly should be stirred, not shaken (James Bond be damned).  If you use a foam brush, brushing too fast will cause bubbles.  Try a long, slow brush stroke, and don't mess with it after you brush it on.

To get rid of bubbles, wait until the poly is well-cured (3 days is best, but no less than 24 hours) and sand with 180 or 220 grit until the bubbles are gone, then re-coat.
Title: Re: bubbles in polyurethane
Post by: beenthere on July 30, 2007, 04:15:37 PM
When the bubbles show up, I use a torch and pass over quickly to get the bubbles to rise to the surface and pop. Especially useful when using the two-part pour-on poly finishes.
But avoiding the bubbles in the can is most important too.
Title: Re: bubbles in polyurethane
Post by: Mooseherder on July 30, 2007, 05:28:49 PM
Quote from: beenthere on July 30, 2007, 04:15:37 PM
When the bubbles show up, I use a torch and pass over quickly to get the bubbles to rise to the surface and pop. Especially useful when using the two-part pour-on poly finishes.
But avoiding the bubbles in the can is most important too.

That's how I do it also. The cheapo Bernz-o-matic torch makes the bubbles disappear quickly and makes a difficult job of making the bubbles come to the surface an easy one.. ;)
Don't try a blow dryer or shrink wrap dryer. It blows the finish into a wrinkle.
Title: Re: bubbles in polyurethane
Post by: Tom on July 30, 2007, 05:53:54 PM
Dragging your brush on the side of the can will load the contents of the can with bubbles too.  If you overload your brush, drag it in a second can.
Title: Re: bubbles in polyurethane
Post by: WDH on July 30, 2007, 10:23:54 PM
Apply it S-L-O-W and S-T-E-A-D-Y.  Let it flow out naturally.  Over application with too many strokes over the same area contributes to bubbles.  A foam brush works very well.
Title: Re: bubbles in polyurethane
Post by: low_48 on July 30, 2007, 10:59:22 PM
Wood species come into play here as well. Open pores, like red oak, have air in them. The poly tries to fill the hole and displaces the air. The air comes up and if the poly is almost flashed over, the air bubble will dry in the finish. Slightly thinning the first coat reduces this.